Squirrel-cage rotor for electric motors.



E. HEITMANN.

SQUIRREL GAGE ROTOR FOR ELECTRIC MOTORS.

APPLICATION FILED JULY 15, 1908.

919,862, Patented A131227, 1909.

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EDWARD HEITMANN, OF MONTOLAIR, NEW JERSEY, ASSIGNOR TO CROCKER-WHEELEl COMPANY, OF AMPERE, NEW JERSEY, A CORPORATION OF NEW JERSEY.

SQUIRREL-CAGE ROTOR FOR ELECTRIC MOTORS.

Specification o Lettrs`1atent.

Patented April 2.7, 1909.

Application filed Juiy 15, 1908. ScriaLNO. 443,713.

To all fw?, om it may concern:

' Beit known that i, EDWARD HEITMANN, a citizen ofthe United States of America, and resident of Montclair, county of Essex, and State of New Jersey, have invented certain new and useful linprov'emen ts in Squirrel- Cage Rotors for Electric hiotors, of which the following is a specilication.

This invention relates to the construction, in' combination with a' laminated. core, of the secondary element in a rotor.V l

The object of this invention is to secure by a rotor of proper design in an induction motor, a machine having-low reactance and high l. starting torque, with high power factor and overload capacity, operating at high current densities, in which both electric iiow and magnetic. linx are Well distributed, avoiding` wrapped with insulation l..

I:harmful eddy currents, which will runcool,

and iii-Which the centrifugal torce tends to increase the electrical and mechanical connection between the rotor bars.

-A further object is to provide a forni inexpensive of manufacture, and with parts easy to assemble and secure firmly so as to forni an electrically Well connected and mechanically rigid structure.

in the acconnianyine sheet of drawings, which forms a part of this application, Figi;- ure l is a perspective View of a rotor for an induction motor embodying my invention.

Fig. 2 is -an elevation of one of the conductor bars, and Fie. 3 is an edsje View of the preferred forni of one of the coils which areeinployed to electrically coi'inect the bars.

its periphery parallel partially closed slotsaA a.

l i i i through which conductor bars B 'B are insertcd, the ends of the bars projecting? bei f ond the core.

bars and nearly ineetthcreby utilizin substantially the entire convex surface of the l core for receiving' the magnetism 'while prefor eddy currents. fordan absolutely reliable ineens for securii rThe portions of the 'bars vyliicn pass through the core laininations arel The bar preferred iorin have' transverse slots i which face the axis of the rotir.

"ilie iipsof the slots are intei L s n I gral with the laniinations and overlap the `of the i -said bars.

spending slots, which are `similarly lettered .in the different bars, When the bars are assol the preferred form, each coil has a plurality -of convolutions c c c2 equal in number to the number of slots at each end of the bars B B and together forming a spiral, each convolution engaging all the corresponding` slots of in that a portion of each convolution sufficient to embrace all the bars is brought truly into a plane of 'rotation and each convolution connected with the adjoining convolution through a short ofset section s s Within the space of two adjoining bars. This has the convenience of ermitting the bars to be eX- actly alike in t e locations of the slots and interchangeable.'

It Will readily be understood that a plurality of slots at each end of the bar, and consequently aplurality of convolutions in the engaging coils are not essential to this invention.

By reason of the slots in the core having The spirall is preferably irregular permanent. overlapping lips the bars are of i necessity inserted endwise through the core slots and before the coilsl are connected thereto. by locked against radial displacement, the engaging coils must be so constructed as not to close on themselves, that is, they must be of such a discontinuous character as Will permit of their being brought. Within the circle ofthe sides of the bars which face the axis of the rotor and then expanded or sprung into engagement with the slots. bars are preferably soldered together to ini sure proper electrical connection. Soldering,

how ver, is not essential to the mechanicalv connection, since there are no mechanical connecting devices were employed. near each end, the slots brinein the sides f (.oiiescrews, bolts or rivets.

strains which would tend to separate the part-S.

`Further advantages in the foregoing construction Whichwill be apparent in view of this description followv from the absence of For this admits of the number oll bars being multiplied to an cxtent which would be inipracticable if such bars may therefore be thinner on account of their being more numerous, therebyd elinii- The coils and The Since, when in the core, they are tlierey nating harmful eddy currents. The multipli-` cationof convolutions in the coils hasa like advantage, and the further advantage of increasing the radiating surface, and thereby also preventing an excessive risel of temperature.

. l/Vhat I claim'as new, and desire to secure by Letters Patent of the United States, is-

l. In a squirrel-cage rotor adapted for use as the secondary element of an induction motor, the combination With a laminated core of conductor bars carried therebyand havin transverse slots near their ends in the sides facing the aXis of the rotor, and coils engaging Said slots and electrically connecting the bars, substantially as described.

2. In a squirrel-cage rotor adapted for use as the secondary element of an induction motor, the combination with a laminated core of conductor bars carried thereby, each of said bars having a lurality of slots near each end in the side Aacing the axis of the rotor, and coils engaging said slots and electrically connecting the bars, substantially as' described.

3. In a squirrel-cage rotor adapted for use as the secondary element of an induction motor, the combination with a laminated core of conductor bars carried thereby, cach of said bars having a plurality of slots near each end in the side facing the axis of the rotor, and coils engaging said slots each of which has a plurality oi' convolutions` and electrically connects the bars, substantially as described.

4. In a squirrel-cage rotor adapted for use as the secondary element of an induction motor, the combination with a laminated core of conductor bars carried thereby, each of said bars having a lurality of slots near each end in the side racing the axis of the rotor, the corresponding slots of `all the bars lying in the saine plane of rotation, and coils having a plurality of convolutions so formed that each convolution engages the corresponding slots, substantially as described.

Signed by me at East Orange, N. J., this 14th day of July, 1908.

. EDWARD HEITMANN.

Witnesses:

SAMUEL AW. BALCH, ARTHUR C. BUNKER. 

